Routine testing for the six non-O157 strains began June 4, and requires raw beef trim to be tested for all seven strains. Under the new rules, the six strains joined E. coli O157:H7 as being classified as adulterants, meaning the products containing them are to be considered unfit for human consumption.

The positive samples represented three non-O157 strains: O26, O103 and O145, according to the USDA.